There are some unique natures that a plasma exhibits. The dispersion relation of an electromagnetic wave propagating in a plasma indicates that the index of refraction ñ of a plasma is less than unity. This means that a plasma is a dispersive medium. If we make a convex plasma lens with the density profile of its maximum at the center of the plasma, the light going through this plasma convex lens will diverge. Some electromagnetic waves such as transverse electric and magnetic (TEM) waves have particular resonant frequencies in propagating through a plasma with a particular density. When this happens, the electromagnetic wave is absorbed into the plasma and disappears by giving off its wave energy to the plasma particles.
Knowing these natures of plasma, if we can design the plasma environment to surround an object in a way that an incoming electromagnetic wave propagates through the plasma but diverges away from the surface of the object or is absorbed in the plasma before it reaches to the surface of the object, then the system with this plasma environment will not be detected by RADAR. This can be done by creating a plasma environment with the appropriate plasma density gradient providing a sufficient deflection of the wave path and with the appropriate plasma density that creates a resonance condition of the incoming wave.
Many different methods to produce plasmas were studied in the past and some methods using microwaves to produce and heat a plasma are invented (Pichot et al. U.S. Pat. No. 4,745,337, Ohara et al. U.S. Pat. No. 5,304,277, Tuda et al. U.S. Pat. No. 6,054,016). These methods vary from a dc discharge method to a laser or an electron beam induced method (H. Conrads and M. Schmidt, “Plasma Generation and Plasma Sources”, Plasma Sources Science Technology 9, 2000, 441-454). Among them, Microwave and Radio Frequency (RF) discharge methods, or High Frequency (HF) discharge methods have extensively been studied. These methods have merits compared to other methods in terms of the quality of plasmas produced, long duration of the device, low cost, simplicity, efficiency and reliability. A high density plasma is obtainable even at atmospheric pressure using these methods and the ion temperature can be controlled over a wide range by applying additional dc fields or RF bias voltage (H. Conrads and M. Schmidt, “Plasma Generation and Plasma Sources”, Plasma Sources Science Technology 9, 2000, 441-454). The life time of these devices is long due to their electrodeless structure. Recently, a method to use electromagnetic surface waves such as surfatrons to produce and sustain plasmas is attaining attention in many areas. Merits using this type of waves to produce and sustain plasmas were addressed and discussed. (H. Conrads and M. Schmidt, “Plasma Generation and Plasma Sources”, Plasma Sources Science Technology 9, 2000, 441-454, M. Moisan and Z Zakrzewski, “Plasma Sources based on the Propagation of Electromagnetic Surface Waves”, J. Phys. D: Appl. Phys. 24, 1991 1025-1048, Milan Siry, Tibor Terebessy and Masashi Kando, “Study of Surface Wave Propagation along the Dielectric Side all in Large-Area Microwave Discharge”, sources unknown)
In the method to produce plasmas using surfatrons, it is common to launch a surface wave along a dielectric tube and to confine a plasma. (H. Conrads and M. Schmidt, “Plasma Generation and Plasma Sources”, Plasma Sources Science Technology 9, 2000, 441-454, M. Moisan and Z Zakrzewski, “Plasma Sources based on the Propagation of Electromagnetic Surface Waves”, J. Phys. D: Appl. Phys. 24, 1991 1025-1048, Milan Siry, Tibor Terebessy and Masashi Kando, “Study of Surface Wave Propagation along the Dielectric Side all in Large-Area Microwave Discharge”, sources unknown) However, it is possible to launch this type of wave into a region where the air is partially and weakly ionized since an electromagnetic wave has a nature to push plasma particles away from it due to its radiation pressure and due to the effect of the ponderomotive force, making a similar condition to the vacuum-plasma boundary in its traveling path. (Nicholas A. Krall and Alvin W. Trivelpiece, “Principles of Plasma Physics”, 1986, San Francisco Press. Inc. ISBN 0-911302-58-1) It is also possible that this pseudo surface electromagnetic wave produces a plasma in an unconfined region and at the same time, it sustains the plasma configuration generated there by obtaining a steady state condition. The use of microwaves to launch as this type of surface waves seems to be promising for this purpose.
If an object is placed in a preconditioned partially and weakly ionized plasma environment and this pseudo surface microwave is launched along the surface of the object but in the vicinity of the surface, a plasma environment with a plasma density gradient is created to surround the object. If this plasma density profile has an appropriate gradient to deflect an incoming electromagnetic wave from the object, this plasma environment can function as a shield to protect the object from being detected by a device that uses reflection of a wave, such as RADAR.
In the prior art, this kind of defense system does not exist. Therefore, I propose a pseudo surface microwave produced plasma shielding system as a defense system, which is a simple electrodeless device that creates a prescribed plasma environment with a prescribed plasma density gradient, and protects an object surrounded by this environment as a shield. This shielding system is not only capable to shield out various electromagnetic waves with various frequencies but it is also capable to shield out an ordinary sound wave by changing the mechanism of wave propagation from a sound wave to an ion acoustic wave in an electromagnetic field environment. It can also protect the object from harmful effects from weapons of mass destruction (WMD) since it can shield out electromagnetic pulses (EMP) created from nuclear explosions against nuclear weapons, instantly change chemical compositions of chemical agents by dissociation and ionization, and instantly kill any kind of virus or bacteria and sanitize the environment against biological weapons. This shielding system also has an extended capability to function as a weapon system to launch plasmiods as a plasma gun as a part of a defense system.
It can further extend its capability to function as a flow field control system to in order to improve flight performance and flight economy of aircrafts, for example, as a boundary layer and turbulence control system, and a lift control system of an airfoil. The use of a plasma flow to control a boundary layer to reduce a drag and noise was studied in the past. (J. R. Roth, D. M. Sherman, S. P. Wilkinson, “Boundary Layer Flow Control with a One Atmospheric Uniform Glow Discharge Surface Plasma”, AIAA 98-0328, 36th Aerospace Sciences Meeting & Exhibit, Jan. 12-15, 1998, Reno, Nev., J. C. Meng, “Wall Layer Microturbulence Phenomenology and a Markov Probability Model for Active Electromagnetic Control of Turbulent Boundary Layers in an Electrically Conducting Medium”, A745692, Jun. 1, 1995, S. Leonov, “Plasma Influence on Characteristics of Aerodynamic Friction and Separation Lines Location”, A517483, September, 2000) For patented inventions, Blackburn et al. U.S. Pat. No. 5,797,563 describes a microwave system to increase aerodynamic efficiency and to decrease the drag force, and Saeks et al. U.S. Pat. No. 6,247,671 describes a method and apparatus to impinge on the shock wave using ions and electrons. However, these systems lack in theoretical explanations and therefore the design aspects to optimize the effect of use of plasma particles in terms of magnetohydrodynamics and plasma physics. The pseudo surface microwave produced plasma shielding system was carefully designed to optimize the effective use of plasma particles from the magnetohydrodynamics and plasma physics point of view.
It has a potential capability to be developed to function as a new type of propulsive device to be replaced with the conventional aircraft engines that use petroleum based fuel. There are a couple of inventions that apply microwave energy to engines. H. Fulenwider, Jr. U.S. Pat. No. 4,064,852 describes a device for pretreatment of vaporizing and heating a liquid fuel using microwave energy before a combustion process and Asmussen et al. U.S. Pat. No. 4,507,588 describes a microwave ion generating apparatus and its application to a space craft engine. However, these devices were not designed to use effective means of heating a propellant and effective means of obtaining a propulsive force. The pseudo surface microwave produced plasma shielding system provides effective means of heating a propellant and obtaining a propulsive force. Overall, this shielding system can offer a simple structure, low cost, low maintenance, long life time, versatile, and flexible defense system and flow field control system.